Summary: In the mid-1980s we carried out a prospective study of early pregnancy in which we enrolled 221 health women who were planning to become pregnant. These women collected daily urine specimens for up to six months. We've assayed these specimens to describe the hormonal events of the menstrual cycle and early pregnancy. 155 women became clinically pregnant during the study, while 44 had pregnancies that ended so early that the pregnancies were detectable only by assay of urinary human chorionic gonadotropin. This unique study has been called a landmark, and continues to provide a rich resource for the description of the earliest stages of pregnancy. (More than 30,000 urine samples are still being stored.) We've published 50 papers from this study over the past two decades, some of which have led to new understanding of the fundamental processes of conception and early pregnancy. In addition, we have continued to make use of large population registries in order to pursue basic questions on pregnancy and maternal and infant health. We have worked especially closely with Norwegian colleagues in the analysis of the Norwegian Medical Birth Registry. Last year's progress. Environmental exposures are often detectable in urine samples. Using urine samples from our Early Pregnancy Study, we have completed feasibility studies demonstrating that bisphenol A and phthalates are detectable in these urines, which have been in freezer storage for more than twenty years. The next step in this project will be to pursue laboratory assays of these contaminants in a broader sample of our urine specimens, so that the exposures can be related to possible increases in the risk of early pregnancy loss and fetal growth. In addition, we have used vital statistics data to explore a more theoretical question, namely the extent to which the mortality among preterm births is due to pathological factors that trigger preterm delivery. Using modeling and empirical data, we estimate that at least half of all deaths among preterm births are due to preexisting pathologic problems. This supports the idea that simple prevention of preterm delivery would not be enough to prevent a large portion of the mortality experienced by preterm babies. More attention needs to be given to the underlying causes of preterm birth rather than simply the event of preterm delivery.